The study on the dynamic rheologieal behavior at molten state for ethylene-propylene-diene terpolymer (EPDM) was conducted with an advanced rheometrie expansion system (ARES)．It was found that dynamic rheological functions such as dynamic storage modulus(G’)

dynamic loss modulus(G″) and dynamic loss tangent (tanδ) at low frequency region can sensitively reflect the change of structure of EPDM．On the basis of the difference of dynamic rheologieal properties between virgin and antioxidant-added EPDM

the characteristic rheologieal behavior of EPDM subjected to annealing was attributed to the thermo-oxidation of EPDM at molten state．The results measured by rheologlcal tests revealed that within the temperature region from 200℃ to 220℃ the thermo-oxidation of EPDM could be detected distinctly．